I have several computers for LAN parties. If I want to buy a game from GOG and run it on multiple computers fror parties, how does this work? Can I download/buy just one copy and put it on multiple computers? Do I need to download it from GOG on each computer, or just copy it from one computer to another? Do I need seperate GOG accounts for each computer?
Thanks,
Andrew V. Romero

GOG games are DRM-free, there is no activation limit, no play limit, no installation limit, nothing.
YOU own your copy of the game, and you're free to do with it what you want - this includes installing it on multiple computers and holding a LAN party.

Direct from the GOG FAQ:
"Can I install one game both on my laptop and desktop PC at home?
Yes. We are not limiting the number of installations or re-installations as long as you are installing your purchased game on PCs in your household. So yeah, if you've got a render-farm in the basement, you might actually break the world record for the number of legal Fallout installations in one household. However, if you think about installing your game on a friend's PC or sharing it with others then please don't do it, okay?"
On the technical side of things, each game is installed from a standalone executable, so you just need to copy this file to any computer you want to install the game on. There's no phoning home, a third-party program, or any kind of authorization required for game installation.

I say it's fine to install on a friends pc as long as you uninstall before his pc leaves your house

It's one of the best features of GOG: it IS DRM-free!
But then again, that PC *is* in your household, non?

If you read the EULA on most (if not all) of GOG's games, you are free to install them on as many PCs as you currently own. If it is not your PC, you cannot legally install it and the owner f that PC should buy their own copy of the game (at 10 bucks or less, what is really stopping you from doing that anyway?). However, as Wec pointed out, if you friend comes over for a LAN party and you install a copy on his machine, there really is nothing illegal about that as long as you remove it when the party is over.

From a legal standpoint this could probably be argued either way (depending on the wording and a court's interpretation of the EULA), but this is a situation where the spirit of the rules is more important than the letter of them. I'd expect that the GOG folks wouldn't have much of an issue with a temporary installation for the duration of a LAN party, as this is only likely to make other people want to purchase the game for their own use if they end up liking it. It's really just a matter of taking a common sense approach to the whole matter and responding in kind to the honest and fair way in which GOG has treated their customers.

You're free to give away or sell your CD copy under the first-sale doctrine (provided that you've uninstalled it from your computer). Reselling or giving away the GOG copy, however, would put you on the wrong side of the law (as the license for the game you purchase from GOG is non-transferable).

I am not a lawyer, but I do have a real interest in software licensing policies.
Firstly, not all games on GOG have the same licence. For example, the EULA of Broken Sword 2 is an agreement between you and GOG, while Heroes of Might and Magic is between you and 3DO, and both have different terms. So the answers to licensing questions will differ for some games on GOG's catalog.
However, let's look at a few clauses from the typical GOG licence:
"Company grants you a non-exclusive, non-transferable license to use the Program"
"Non-transferable" is the key word here. By accepting the EULA, you agree not to transfer your game to other people.
From a legal standpoint, you should have "right of first sale" on your CD copy, which means that you can always give/sell your copy to someone else, unless it's specifically prohibited in the EULA that accompanied your boxed product (whether they can legally prohibit this is a completely different question). So you can always give away or sell the CD copy.
On the other hand, the licence from GOG states (as shown above) that your game download is non-transferable. This is the case for just about every digital distribution platform (though I understand that Impulse are planning on implementing features to allow transfer of game licences).
According to the agreement you make with GOG, you cannot allow someone else to install your GOG copy.
Zolgar, I completely agree that what you're asking about is morally sound, but that's what I see from a legal standpoint.
"This Program is licensed, not sold, for your personal, non-commercial use.". The definition of "personal" is not detailed here, but I imagine that it does not extend to installing it on 6 computers to play at a LAN party.
For the purposes of a LAN party or multiplayer gaming session over the internet, the EULA would seem to indicate that it would be appropriate for each player to purchase their own copy of the game. At $6-$10 per game, this seems quite reasonable.
If you're interested in purchasing multiple copies of the same game without creating an account for each person, that might be an interesting question for the GOG team.
And one final excerpt from the EULA which I find pertinent:
"6.Injunction. Because Company would be irreparably damaged if the terms of this Agreement were not specifically enforced...
The way GOG games are distributed means that you could, theoretically, install them on a hundred computers for a really big LAN party.
My point is that you shouldn't. GOG distributes games for companies that have a lot of lawyers, and who would probably cancel their publishing agreement if they believed that games sold through GOG were being used irresponsibly. GOG really could be irrepairably damaged if its licences were abused.

I think what people are missing is a key difference.
I did not "give" nor "sell" the copy of the game, but "lend" it. He has since finished, and uninstalled (thus "returned"), the game.
So the end effect was allowing him to borrow my copy of the game.. without having to worry about juggling CDs.

Unfortunately some EULAs strictly disallow lending as well. Not looking to argue, just saying. :|

Lending actually typically requires an additional licensing agreement with the rights holder, so doing so would actually probably just land you in more trouble if the matter came to court. However, it's more likely the law would simply regard such non-commercial lending as a transfer of ownership from you to your friend, then from your friend back to you (which is basically what it is, with a gentleman's agreement that your friend would give the game back after using it).
Trying to split hairs on the legality of the matter, however, is a pretty pointless exercise. If the matter comes to court, chances are you're fucked. But since it very likely isn't going to come before a court then why worry about it? If you don't think there's any ethical or moral problem with what you're doing, then what's the issue, regardless of what the law says? And if you do feel that there's some ethical problem, and that's what's prompting the legal hair-splitting, then just stop trying to find an excuse and stop doing what you see as wrong. Just take a common sense approach to the whole matter, and leave the mess of legal codes to the lawyers in the cases where the matter actually comes before a court.

Agreed. I'm pretty sure GOG doesn't mind you lending copies of the game for a LAN party; gets more word out for the service! Just make sure not to just give them copies of all your GOG games to keep, though. That would not be a very nice thing to do to the GOG and CD Projekt people.

Resale and giving away (lending would be giving away temporarily) are covered however under the first sale doctrine of copyright law (in the US), so in the US at least, the predominate case law in the courts has been that you may give away and sell your software, even if the publisher says otherwise. "Lending" of course implies that you have removed all copies of it from your computer before doing so, which doesn't really cover the LAN party situation.